In the course of drilling, completing, and producing subterranean reservoirs, operators find it necessary to rig up and run into a well various types of work strings. Examples of work strings include, but are not limited to, drill strings, coiled tubing, snubbing pipe, electric line, production tubing, and wireline.
When working with subterranean reservoirs, operators are always concerned about the high pressure that may exist in such reservoirs. These high pressures may reach several thousands of pounds per square inch. Thus, during any type of operation involving work strings that are run into a well, operators will employ various types of valves at the surface of the well to isolate the crew members working on the well from the high pressure within the reservoir.